Typically, a device responsible for routing data through a computer network, such as a router, implements one or more intra-network routing protocols commonly referred to as interior gateway protocols (IGPs) to exchange so-called “routing information” describing links or paths within the network domain. Example IGPs include an Intermediate System to Intermediate System (IS-IS) routing protocol and an Open Shortest Path First (OSPF) routing protocol. Each router may then resolve the routing information by selecting a path through the network for reaching each available destination within the network and generating forwarding information, which may be used to forward data packets through the computer network.
Both the IS-IS and OSPF routing protocols fall within a class of routing protocols referred to as link-state protocols. Link state protocols advertise or otherwise facilitate the exchange of routing information by generating and transmitting link state advertisements (which may also be referred to as “Link State Protocol Data Units”) describing a state of a link between any two adjacent routers within the computer network. These link state advertisements may include information identifying an interface cost or metric associated with an interface to which the link connects and a link cost or metric associated with the link, as well as a color or administrative group associated with the link and any other constraints commonly employed for selecting a path through a network in accordance with a link state protocol. The administrative group associated with the link (often referred to as a “color” or resource class for the link) may provide a way by which an administrator can control path selection.
For example, an administrator may assign one or more links a color of “red” and another one or more links a color of “blue.” The administrator may then configure the path selection algorithm that selects from among the entire set of paths determined via link state advertisements to utilize only links that are associated with the color “red” for one customer and to utilize only links that are associated with the color “blue” for another customer. In this manner, the administrator may configure groups of links for different uses. Commonly, administrators utilize these colors to differentiate between links that cannot be differentiated by more objective metrics. In this way, the color or administrative group fields of link state advertisements enable what may be considered a more subjective metric or constraint of path selection. The growth of networks and the increase in the number of network devices has complicated administration beyond what the developers of these protocols imagined. In some instances, these protocols may fail to adequately accommodate a large number of administrative groups, which may burden administration of larger networks by limiting how path selection is performed.